Everything You Need to Know About Temperature Control Fluids


Choosing the right medium plays a decisive role for the results of the temperature control process. Reliable operation and optimum heat transfer efficiency can only be guaranteed if temperature control instrument, bath fluid and application are optimally matched to each other.

JULABO Thermal bath fluids are carefully selected and long-term tested media with ideal thermodynamic properties for a variety of applications. They are optimally designed and suitable for temperature applications in JULABO instruments.

Which bath fluid do I need?

The most important criterion for safe selection is the working temperature range of the application. All other properties of JULABO Thermal fluids, such as viscosity, oxidation behavior, and heat conductivity, are ideally adjusted for use with JULABO temperature control instruments. 

Technical terms for JULABO Thermal bath fluids

The recommended working temperature range specifies the lowest and highest temperature for the use of the respective bath fluid. Exact and stable operation of your JULABO instrument is guaranteed within the given range over a long period.

The specific heat capacity is the thermal energy required to raise the temperature of 1 kg of liquid by 1 K.

The viscosity indicates the flow characterictics of the bath fluid and is highly temperature-dependent. When operating a JULABO instrument, the viscosity has a decisive influence on temperature stability and pump performance.

The fire point is the temperature at which bath fluids continue to burn after ignition (>5 sec). According to standards, the maximum working temperature must always be 25 °C below this fire point. (Exception: closed systems from JULABO).

The flash point is the lowest temperature at which emerging vapors can temporarily ignite (<5 sec). The highest operating temperature specifications for JULABO bath fluids are always below the flash point and therefore exclude these risks. (Exception: closed systems from JULABO).

The boiling point is the temperature at which a fluid starts to boil (with an ambient pressure of 1 bar).

The ignition temperature is the lowest temperature at which the bath fluid ignites spontaneously and continues to burn without heat supply.

In closed JULABO systems, there is no contact between the bath fluid and oxygen in the ambient air. Therefore, the flash and fire point indicated for these systems can be easily exceeded. Due to its construction, contact to ambient air cannot be avoided in the internal expansion tank. To avert the danger of ignition, the expansion tank of JULABO instruments is actively cooled (cold oil superimposition).


Use the thermal expansion coefficient to determine the expansion of the bath fluid in your application. Based on your average working temperature you can define the average density (see the density diagram of the relevant bath fluid) Now you can calculate the expansion using the formula below. The result will help you when sizing an expansion vessel. Please note: The filling volume is more than just the volume in the JULABO instrument. The volumes in the application and hoses must also be taken into account in this calculation.

Water as bath fluid

Depending on the application, water can also be used as a bath medium. Here, it must be considered whether the instrument can work with water in the first place and, if so, whether the working temperature range and water quality meet JULABO specifications. Inadequate water quality can lead to calcification or corrosion of system-relevant components and thus to failure of the instrument. To be avoided at all costs: Hard water, water that contains iron or chlorine, distilled or de-ionized water, seawater or water that comes from cooling towers or rivers. Further details can be found in the operating manual of the respective JULABO instruments.

We generally recommend consulting our experts before using water as a bath medium.

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We definitely have the perfect medium for your temperature control instrument and your application in our portfolio. If you need further support with your selection, our product and service team will be happy to help.

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